Organization of the blood system of rhynchonellid brachiopod Hemithiris psittacea (Brachiopoda: Rhynchonelliformeaстатья
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Дата последнего поиска статьи во внешних источниках: 1 мая 2024 г.
Аннотация:The brachiopods are sessile invertebrates with an unusual blood system, whichconsists of a long‐branched dorsal vessel. It is still unknown how blood circulates inthis system. In the present study, for the first time we propose the circulation ofblood in brachiopodHemithiris psittaceabased on morphological and experimentaldata. The main heart is located on the dorsal side of the stomach and divides thedorsal vessel into anterior and posterior parts. The anterior part enters thelophophore, where it gives off blind branches to each tentacle. The posterior partpasses by the funnels of the nephridia and forms a blindly closed network in thegonads. We suggest that the circulation of blood includes three successive stages.During the first phase of systole of the main heart, blood flows through the anteriordorsal vessel. During the second phase of systole, blood flows through the posteriordorsal vessel. During diastole, blood flows from the anterior and posterior vessels and fills the main heart. The origin of a peculiar blood system in brachiopods can be explained by reduction of the ventral vessel, which is probably correlates with there duction of the ventral side of the brachiopod ancestor's body. Another peculiarity of brachiopod blood system is the presence of an ampullar heart, which functions asa blood depot and allows blood to move in the vessels in two directions in an oscillatory mode. The brachiopod blood system contains essels lacking true endothelium and can be classified as an“incompletely closed”type.